Not to argue with a sage like Rothenberg, but what exactly makes Bayh so nightmarish for Republicans? He's good looking, sure, but no more so than Edwards, and he's certainly not a better speaker. He's hawkish, sure, but no more so than was Lieberman, and look where that got him. He's not a general, like Clark, nor a superstar, like Hillary. Labor doesn't love him, nor does any other interest group. And, in this era of calcified partisanship, or Republicans really going to be marking his ballot box en masse? What if the right runs a Hagel, or McCain? And what makes Bayh, who's going to have to swing left in the primary in order to calm a nervous base, stronger than other popular Democratic Southerners (for our purposes, same as Midwesterners) like Warner or Bredesen?
Bayh might be a fine candidate, but Rothenberg is hanging his hat entirely on perceived moderation, as if the simple air of centrism was enough to guarantee election. Call it Clinton-syndrome. But Clinton won with a hefty dose of populist rhetoric and blurrily liberal lines -- I've seen no evidence that Bayh is as skilled an illusionist. So lets not build him a White House in the sky before we see anything from the guy. His current selling points are looks, geography, and moderation. Enough to make him interesting, but not nearly enough to make him unstoppable.
(If there's one thing we know about comment trolls, it's that they're lazy)